Some new models of real and ideal gas

Simple discrete probabilistic models of gas in dimension one and three are defined, described and studied.     

Bipartite entanglement of a two-qubit system with anisotropic couplings under nonuniform magnetic fields

This paper investigates bipartite entanglement of a two-qubit system with anisotropic couplings under an inhomogeneous magnetic field. This work is mainly to investigate the characteristics of a Heisenberg XYZ chain and obtains some meaningful results. By the concept of negativity, it finds that the inhomogeneity of magnetic field may induce entanglement and the critical magnetic field is independent of J_z. The inhomogeneous magnetic field can increase the value of critical magnetic field B_c. It also finds that the magnetic field not only suppresses the entanglement but also can induce it to revival for some time.     

Bipartite entanglement in the spin-1/2 Ising-Heisenberg planar lattice constituted of identical trigonal bipyramidal plaquettes

The bipartite entanglement is rigorously examined in the spin-1/2 Ising-Heisenberg planar lattice composed of identical inter-connected bipyramidal plaquettes at zero and finite temperatures using the quantity called concurrence. It is shown that the Heisenberg spins of the same plaquette are twice stronger entangled in the two-fold degenerate quantum ground state than in the macroscopically degenerate quantum chiral one. The bipartite entanglement with chiral features completely disappears below or exactly at the critical temperature of the model, while that with no chirality may survive even above the critical temperature of the model. Non-monotonous temperature variations of the concurrence clearly evidence the activation of the entangled Heisenberg states also above classical ground state as well as their re-appearance above the critical temperature of the model.     

Non-uniform pressure driven cylindrical compression of ideal gases and real matter

The numerical study of the implosion of a cylinder driven by an azimuthally varying pressure has shown that two regimes can exist for the evolution. In the first regime cylinder implodes almost symmetrically, while in the second regime energetic jets appear behind the shock wave, thus destroying the implosion uniformity. Scaling laws for the threshold of the transition between these two regimes are given as a function of the relevant dimensionless parameters for both ideal gases and real matter.     

Intramolecular association within the SAFT framework

A general theory for modelling intramolecular association within the SAFT framework is proposed. Sear and Jackson [Phys. Rev. E. 50 (1), 386 (1994)] and Ghonasgi and Chapman [J. Chem. Phys. 102 (6), 2585 (1995)] have previously extended SAFT to include intramolecular association for chains with two sites. We show that the resulting equations from the two approaches are equivalent, and use their work as a basis for developing a new general theory. The approach used by Ghonasgi and Chapman is based on mass balances and an infinite dilution result and provides the equations needed to determine the contribution to the Helmholtz free energy from association (inter- as well as intramolecularly) at equilibrium. Sear and Jackson rederived the contribution to the Helmholtz free energy from association from the theory by Wertheim [J. Stat. Phys. 42 (3–4), 459 (1986)] with inclusion of intramolecular association, and using this approach we obtain an expression for the Helmholtz free energy that is valid also at non-equilibrium states (with respect to hydrogen bonds), which is very useful when calculating derivatives.     

Calculations of the propagator within the tomographic-probability framework

We show that the ambiguity in choosing the tomographic propagator for an evolving linear quantum system is related to the homogeneity properties of the system symplectic tomogram. We study in detail an example of the driven harmonic oscillator. We prove that two formally different propagators of the quantum kinetic equation for the oscillator are identical on the domain of homogeneous tomographic probability distributions.     

The real and complex Lorenz equations in rotating fluids and lasers

The Lorenz equations are derived systematically from amplitude equations of weakly nonlinear dispersively unstable physical systems near criticality when weak dissipation is added. This derivation is only valid if the undamped neutral curve is not destabilised by the addition of weak dissipation. The addition of extra weak dispersive effects make some of the coefficients complex and yields a complex set of Lorenz equations. Both sets of equations are derived in examples in laser optics and baroclinic instability.     

Light elementary pseudoscalars within the framework of effective lagrangians

The total, effective, low energy lagrangian for K→π+ pseudoscalar decays has been derived for any model involving light elementary pseudoscalars. As an illustration, branching ratios for those decays have been calculated for a two-Higgs doublet model in which only one Higgs doublet couples to quarks. Experimentally allowed regions in the parameter space have been found.     

Elastic modulus,surface tension,adhesion, and ideal and real strengths of solids

Formulas for the surface tension coefficient, adhesion energy, elastic modulus, and strength of solids versus the atomic density have been derived. The theoretical values of these parameters have been confirmed by experimental data gathered from many metals, insulators, and semiconductors.     

Leptoquark mechanism of neutrino masses within the grand unification framework

We demonstrate the viability of the one-loop neutrino mass mechanism within the framework of grand unification when the loop particles comprise scalar leptoquarks (LQs) and quarks of the matching electric charge. This mechanism can be implemented in both supersymmetric and non-supersymmetric models and requires the presence of at least one LQ pair. The appropriate pairs for the neutrino mass generation via the up-type and down-type quark loops are \(S_3\)–\(R_2\) and \(S_{1,\,3}\)–\(\tilde{R}_2\), respectively. We consider two distinct regimes for the LQ masses in our analysis. The first regime calls for very heavy LQs in the loop. It can be naturally realized with the \(S_{1,\,3}\)–\(\tilde{R}_2\) scenarios when the LQ masses are roughly between \(10^{12}\) and \(5 \times 10^{13}\) GeV. These lower and upper bounds originate from experimental limits on partial proton decay lifetimes and perturbativity constraints, respectively. Second regime corresponds to the collider accessible LQs in the neutrino mass loop. That option is viable for the \(S_3\)–\(\tilde{R}_2\) scenario in the models of unification that we discuss. If one furthermore assumes the presence of the type II see-saw mechanism there is an additional contribution from the \(S_3\)–\(R_2\) scenario that needs to be taken into account beside the type II see-saw contribution itself. We provide a complete list of renormalizable operators that yield necessary mixing of all aforementioned LQ pairs using the language of SU(5). We furthermore discuss several possible embeddings of this mechanism in SU(5) and SO(10) gauge groups.     

Quantum electrodynamics within the framework of a new four-dimensional symmetry

We discuss quantum electrodynamics within the framework of a new four-dimensional symmetry in which the concept of time, the propagation of light, and the transformation property of many physical quantities are drastically different from those in special relativity. However, they are consistent with experiments. The new framework allows for natural developments of additional concepts. Observers in different frames may use the same grid of clocks, located in any one of the frames, and hence have a universal time.I dedicate this paper to the memory of my beloved father, Hsu Mau-Yuen (1903–1977), whose understanding helped me choose to work on physical problems.Work supported in part by the ERDA, Contract No. E(40-1)3992 and by NASA.     

The network of scientific collaborations within the European framework programme

We use the emergent field of complex networks to analyze the network of scientific collaborations between entities (universities, research organizations, industry related companies,…) which collaborate in the context of the so-called framework programme. We demonstrate here that it is a scale-free network with an accelerated growth, which implies that the creation of new collaborations is encouraged. Moreover, these collaborations possess hierarchical modularity. Likewise, we find that the information flow depends on the size of the participants but not on geographical constraints.     

Analysis of optical crosstalk within optoelectronic integrated circuits including lasers and photodetectors

Optical crosstalk from a 1.3 μm laser to a 1.55 μm photodiode on a single InP substrate, and its suppression within 1.3 μm/1.5 μm Y-junction transceiver OEICs, has been analyzed experimentally. The results indicate that the optical crosstalk suppression is limited by the accumulated light in the OEIC substrate coming mainly from the spontaneous emission of the integrated laser and from stray light at the laser–waveguide butt joint interface. For OEICs, integrating lasers and photodetectors, the achievable optical intra-chip crosstalk at present will be in the range of 30–40 dB at the required small die dimensions. Received: 16 May 2001 / / Published online: 23 October 2001     

Local modes of silane within the framework of stretching vibrational polyads

We define stretching relative equilibria (RE) of silane and other similar tetrahedral molecules in terms of the dynamical polyad symmetry which assumes the resonance condition 1:1 between the two stretching vibrational modes ν₁ and ν₃ of the molecule. Exploiting symmetry and topology arguments and reducing the dimension of the classical mechanical system, we find these RE. One of them, with local symmetry C_3v and minimal energy within a polyad, corresponds to the local modes. We give the upper energy limit of the local mode localization within a polyad.     

Binding energy produced within the framework of the accretion of millisecond pulsars

The role and implication of binding energy through the accretion-induced collapse (AIC) of accreting white dwarfs (WDs) for the production of millisecond pulsars (MSPs) are investigated. The binding energy model is examined due to the dynamic process in closed binary systems, and the possible mass of the companion sufficient to induce their orbital parameters is investigated. The deterministic nature of this interaction has a strong sensitivity to the equation of state of the binary systems (where the compactness of a neutron star is proportional to the amount of binding energy) associated with their initial conditions. This behavior mimics the commonly assumed mass and amount of accreted matter under the instantaneous mass loss (\begin{document}$\Delta M \sim 0.18M_{\odot}$\end{document}). As a result, this indicates an increase in the MSP's gravitational mass due to angular momentum losses. The outcome of such a system is then a circular binary MSP in which the companion is a low-mass WD, thus distinguishing the binary formation scenarios. In addition, the results of this work could provide constraints on the expected mass and binding energy of a neutron star based on the accretion rate.     

Possible structures of the neutral current within a gauge theory framework

We examine a class of gauge theories based on U(1)×SU(2)×G allowing for an arbitrary number of gauge bosons, while retaining the lowq ² four fermion interaction of the standard model. Measurable consequences fore ⁺ e ^?→μ ⁺ μ ^? ande ⁺ e ^?→e ⁺ e ^? at presently available as well as LEP energies are presented. Implications of the recently determined QED cut-offΛ _? ? 100 GeV on gauge boson properties and the anomalous magnetic moment of the muon are pointed out.